1. Field of the Invention
This invention relates generally to apparatus for compensating for the structural vibration of a missile in flight. More particularly, the present invention relates to an adaptive body-bending estimator which will substantially reduce the amount of undesirable energy passed through the autopilot during flight.
2. Description of the Prior Art
During flight a missile passively vibrates at its structural natural frequencies. Generally, this passive vibration is not a problem, unless the missile's autopilot couples the missile body sensors with the control actuation system of the missile. The missile's autopilot coupling of the sensors with the actuators generates a feedback loop which actively amplifies missile vibrations. The amplified missile vibration can adversely affect missile performance during flight which may result in the missile missing its target. For example, missile vibrations can cause degradation in seeker performance, reduction in the range of the missile, and accelerated consumption of the missile actuation system's energy source.
A solution used in the past to solve this problem is to utilize notch filters to reduce the amount of undesirable energy passed through the autopilot. This approach, however, requires either (1) a prior knowledge of the structural frequencies of the missile, or (2) an estimation technique to identify the correct frequencies during the missile's flight.
Adjustable notch frequencies scheduled as a function of time generally work whenever a missile's structural frequencies are known and well characterized. Unfortunately, accurate predictions of the missile's structural frequencies are generally not available. This is especially true for missile developmental programs which may include uncertainties in the frequency profile due to inadequacies in testing and computer modeling.
Accordingly, there is a need for an adaptive body-bending estimator which compensates for the undesirable coupling of a missile's structural vibration through the missile autopilot which, in turn, adversely effects the missile performance during flight.